export default {
  bind(el, binding, vnode) {
    const dialogHeaderEl = el.querySelector('.el-dialog__header')
    const dragDom = el.querySelector('.el-dialog')
    dialogHeaderEl.style.cssText += 'cursor:move;'
    dragDom.style.cssText += 'top:0px;'

    // 获取原有属性 ie dom元素.currentStyle 火狐谷歌 window.getComputedStyle(dom元素, null);
    const getStyle = (function() {
      if (window.document.currentStyle) {
        return (dom, attr) => dom.currentStyle[attr]
      } else {
        return (dom, attr) => getComputedStyle(dom, false)[attr]
      }
    })()

    dialogHeaderEl.onmousedown = (e) => {
      // 鼠标按下，计算当前元素距离可视区的距离
      const disX = e.clientX - dialogHeaderEl.offsetLeft
      const disY = e.clientY - dialogHeaderEl.offsetTop

      // const dragDomWidth = dragDom.offsetWidth;
      // const dragDomHeight = dragDom.offsetHeight;
      //
      // const screenWidth = document.body.clientWidth;
      // const screenHeight = document.body.clientHeight;

      // const minDragDomLeft = dragDom.offsetLeft;
      // const maxDragDomLeft = screenWidth - dragDom.offsetLeft - dragDomWidth;
      //
      // const minDragDomTop = dragDom.offsetTop;
      // const maxDragDomTop = screenHeight - dragDom.offsetTop - dragDomHeight;

      // 获取到的值带px 正则匹配替换
      let styL = getStyle(dragDom, 'left')
      let styT = getStyle(dragDom, 'top')

      if (styL.includes('%')) {
        styL = +document.body.clientWidth * (+styL.replace(/%/g, '') / 100)
        styT = +document.body.clientHeight * (+styT.replace(/%/g, '') / 100)
      } else {
        styL = +styL.replace(/\px/g, '')
        styT = +styT.replace(/\px/g, '')
      }

      document.onmousemove = function(e) {
        // 通过事件委托，计算移动的距离
        const left = e.clientX - disX
        const top = e.clientY - disY

        // 边界处理
        // if (-left > minDragDomLeft) {
        //   left = -minDragDomLeft;
        // } else if (left > maxDragDomLeft) {
        //   left = maxDragDomLeft;
        // }
        //
        // if (-top > minDragDomTop) {
        //   top = -minDragDomTop;
        // } else if (top > maxDragDomTop) {
        //   top = maxDragDomTop;
        // }

        // 移动当前元素
        dragDom.style.cssText += `;left:${left + styL}px;top:${top + styT}px;`

        // emit onDrag event
        vnode.child.$emit('dragDialog')
      }

      document.onmouseup = function() {
        document.onmousemove = null
        document.onmouseup = null
      }
    }
  }
}
